 IVES 9 IVES Conference Series 9 Evolution of flavonols during Merlot winemaking processes

Evolution of flavonols during Merlot winemaking processes

Abstract

Aim: The phenomenon of quercetin precipitation in wine (flanovol haze), has been manifested for many years in several wine-producing regions, such as Italy, Australia, and New Zealand (Gambuti et al., 2020; Lanati, Marchi, & Cascio, 2014; Somers & Ziemelis, 1985). Due to the limited information related to the quercetin aglycone behavior and its precursors during wine production in New Zealand, this study aims to monitor the evolution of flavonols and other polyphenols during the commercial fermentation of Merlot grapes, using different fermentation conditions, and vineyard treatments.

Methods: Various trials evaluating sun exposure, winemaking practices, and winemaking process management were undertaken using Merlot grapes, commercial yeast cultures, potassium metabisulphite (20 g/hL), and nutrient supplementation with DYNASTART®-LAFFORT at 20 g/hL. Samples were taken through the winemaking stages, and the polyphenols were quantified using a reversed-phase HPLC method (Garrido-Bañuelos et al., 2019; Peng et al. 2002).

Results: Grapes with elevated amounts of flavonols glycosides produced wines with higher levels of flavonol glycosides and quercetin. Wines made from grapes with greater sun exposure ended up with more flavonol glycosides (89 mg/L) and quercetin (16 mg/L) than the wines elaborated from less exposed grapes (47 mg/L and 9.4 mg/L, respectively). Certain winemaking practices showed differences in quercetin content, for example using small fermentation (250 kg) (12 mg/L), and large fermentation (five tonnes) (28 mg/L). The data also indicates that tannins and total anthocyanins were present at 786 mg/L and 156 mg/L, respectively, for small-scale ferments, and at 888 mg/L and 363 mg/L, respectively, for large-scale ferments. In evaluating the winemaking process management, the ferment pumped over (largest fermentation volume) exhibited flavonol glycosides and quercetin at the highest concentration (91 mg/L and 20 mg/L, respectively), compared to the remaining treatments. PMS, enzyme, and PMS plus enzyme, additions lowered the concentration of the flavonols glycosides at the end of the winemaking process (37 mg/L, 42 mg/L, and 43 mg/L, respectively). It was seem that the PMS plus enzyme (15.6 mg/L) increase quecetin in wine when compared to the control, no additions, (12.6 mg/L). The wines treated with enzyme, PMS, and PMS plus enzyme, also had lower concentrations of anthocyanins (215 mg/L, 233 mg/L, and 238 mg/L, respectively) than the control (291 mg/L).

Conclusions

The study confirmed past research on the role of sun exposure in the formation of flavonols in Merlot grapes and wines. Fermentation size can improve the extraction of polyphenols into wine, and the enzyme additions can promote the hydrolysis of flavonol glycosides. In considering winemaking practices to lower flavonol content, the impact on remaining wine phenolics, of importance to wine colour and mouthfeel, also needs to be carefully evaluated.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Cristian Hernandez

School of Chemistry University of Auckland,Paul KILMARTIN, School of Chemistry, University of Auckland Leandro DIAS, School of Food Science, University of Auckland Gianni FLEGO, Villa Maria Estate winery Rebecca DEED, School of Biological Sciences, University of Auckland

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Citation

Making sense of available information for climate change adaptation and building resilience into wine production systems across the world

Effects of climate change on viticulture systems and winemaking processes are being felt across the world. The IPCC 6thAssessment Report concluded widespread and rapid changes have occurred, the scale of recent changes being unprecedented over many centuries to many thousands of years. These changes will continue under all emission scenarios considered, including increases in frequency and intensity of hot extremes, heatwaves, heavy precipitation and droughts. Wine companies need tools and models allowing to peer into the future and identify the moment for intervention and measures for mitigation and/or avoidance. Previously, we presented conceptual guidelines for a 5-stage framework for defining adaptation strategies for wine businesses. That framework allows for direct comparison of different solutions to mitigate perceived climate change risks. Recent global climatic evolution and multiple reports of severe events since then (smoke taint, heatwave and droughts, frost, hail and floods, rising sea levels) imply urgency in providing effective tools to tackle the multiple perceived risks. A coordinated drive towards a higher level of resilience is therefore required. Recent publications such as the Australian Wine Future Climate Atlas and results from projects such as H2020 MED-GOLD inform on expected climate change impacts to the wine sector, foreseeing the climate to expect at regional and vineyard scale in coming decades. We present examples of practical application of the Climate Change Adaptation Framework (CCAF) to impacts affecting wine production in two wine regions: Barossa (Australia) and Douro (Portugal). We demonstrate feasibility of the framework for climate adaptation from available data and tools to estimate historical climate-induced profitability loss, to project it in the future and to identify critical moments when disruptions may occur if timely measures are not implemented. Finally, we discuss adaptation measures and respective timeframes for successful mitigation of disruptive risk while enhancing resilience of wine systems.

Evolution of the amino acids content through grape ripening: Effect of foliar application of methyl jasmonate with or without urea

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Local adaptation tools to ensure the viticultural sustainability in a changing climate

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Photoselective shade films affect grapevine berry secondary metabolism and wine composition

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